Approximately 8% of children in the United States are diagnosed with Specific Language Impairment (SLI). In addition to problems acquiring morphology and syntax, a significant number of children also demonstrate difficulty acquiring vocabulary. Vocabulary deficits are particularly devastating in young children because lexical acquisition is strongly associated with later language and literacy development. Currently we lack methods for diagnosing specific word learning problems in individual children and have little treatment efficacy data to guide intervention. The primary goals of this research are to develop methods for identifying the individual word-learning deficits of young children with SLI and to evaluate prescriptive treatments targeting those deficits. The research plan is based on the premise that word learning may be compromised by processing deficits in one or more lexical levels including the conceptual, lexical-semantic, or phonological. A series of four cross-sectional and one longitudinal study will test the hypothesis that phonological and/or semantic encoding or retrieval cues designed to improve the storage or retrieval of lexical-semantic or phonological level representations of words improves word learning in preschoolers with SLI. Specific Aims: (1) Document the effect that phonological or semantic encoding cues have on fast mapping and (2) word learning rate. (3) Document the effect that sequencing phonological then semantic encoding cues have on word production. (4) Document the effect that phonological or semantic retrieval cues have on word production. (5) Document, longitudinally, the efficacy of prescriptive treatments derived from studies 1-4for preschoolers receiving small-group instruction during the academic year preceding kindergarten. Significance: This research program that will increase our theoretical understanding of the underlying deficits of specific language impairment and will develop new treatments to help children reach their full potential by improving language growth, positively impacting children's qualify of life and significantly increasing their likelihood of school success.